docs: def _sample_mvn(n_samples, cov, prng):
      """Draw a multivariate normal sample from the graph defined by cov.
  
      Parameters
      -----------
      n_samples : int
  
      cov : matrix of shape (n_features, n_features)
          Covariance matrix of the graph.
  
      prng : np.random.RandomState instance.
      """
      n_features, _ = cov.shape
      return prng.multivariate_normal(np.zeros(n_features), cov, size=n_samples)